The present invention relates to an ammeter device including circuitry for accurately measuring a small electric current and capturing the peak current reading that occurs during a selected time interval. The design, then, is particularly adapted for measuring small discharge currents, for example, from a charged capacitor or from a small battery having a high internal resistance. In accomplishing this, the device measures the polarity of the discharged current.
The construction of the device is particularly adaptable for measuring small discharge currents generated by an amalgam dental filling located in the human mouth. As can be appreciated, an amalgam filling is composed of two or more dissimilar metals, and the filling is subjected to an acidic bath in the form of saliva. That being the case, a filling functions as a small battery having a high internal resistance. When an electrical connection is made between the amalgam filling and the moist fleshy tissues of the mouth, a small discharge of electrical current is observed. After discharge, the amalgam filling will slowly build up its electrical charge, which usually takes several minutes.
This discharge current is normally in the range of several microamps, and may also have a positive or negative polarity. Further, observation of specific electrical activity of the filling for the matrix of fillings has indicated that this electrical activity can potentially have an impact on the health of the person in whose mouth the filling exists both as a result of the electrical current itself and as a result of the current's effect on toxic metals which may form the amalgam.
Existing ammeters, while technically usable for measuring the current generated by a particular filling, have some shortcomings in providing repeatable, accurate test results, for two reasons. First, traditional ammeters measure RMS voltages which are proportional to the current source. In measuring the discharge from a filling, however, it is desirable to have a peak voltage measurement rather than an RMS measurement. Second, in measuring discharge current from a filling, it is desirable to measure the maximum current, that is, the peak current value, which necessitates a way of capturing that maximum value. Existing ammeters fluctuate with the current passing therethrough, so that is is necessary for an observer to visually note the highest reading that occurs during the particular time interval of current discharge. Such is not convenient in the measuring of a discharge current, since the discharge occurs immediately upon making electrical connection between the fleshy tissues and the filling and occurs in an inverval of about 0.2 to 0.5 seconds. Observation of this phenomenon normally requires two technicians, one to make the required contacts in the mouth of the patient and the other to monitor the ammeter.
Accordingly, there is a need for an ammeter that can measure a peak discharge current and which can capture the maximum value of the reading of a current discharge from the current source. This need includes such a device that displays the maximum value for a reasonable period of time allowing a single operator to activate discharge and then subsequently record the discharge data. Further, there is a need for such devices that can cycle through repetitive steps so that a series of measurements can be taken in an easy, convenient manner.